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Fooled by Randomness - The Hidden Role of Chance in Life and in the Markets by N.pdf
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读完之后最大的感受就是：（1）如果有1万个同学一起读书，那么总有那么几个能够很成功。虽然如果算概率，1/10000，会说这个同学的成功是非常特殊的，他或者她一定很聪明或者付出了很多努力。但是，本书作者认为，大样本的情况下，这种事件的发生其实很有可能，毕竟不是1万个同学都成功了。（2）在考虑收益和损失的概率时，如果损失的金额很大，即使概率很小，也应该避免。（3）只有不依赖过去的成功，躺在功劳簿上，不断地学习和挑战自己的人，才会赢得作者的尊重。
以下是部分摘抄（发帖长度有限制）：
Table 1 Table ofconfusion
| GENERAL | |
| Luck | skills |
| Randomness | determinism |
| Probability | Certainty |
| Belief, conjecture | Knowledge, certitude |
| Theory | Reality |
| Anecdote, coincidence | Causality, law |
| forecast | Prophecy |
| MARKET PERFORNACE | |
| Lucky idiot | Skilled investor |
| Survivorship bias | Market outperformance |
| FINANCE | |
| Volatility | Return (or drift) |
| Stochastic variable | Deterministic variable |
| PHYSICS AND ENGINEERING | |
| Noise | Signal |
| LITERARY CRITICISM | |
| None (literary critics do not seem to have a name for things that they do not understand) | Symbol |
| PHILOSOPHY OF SCIENCE | |
| Epistemic probability | Physical probability |
| Induction | Deduction |
| Synthetic proposition | Analytic proposition |
Part A Solon's warning - skewness, asymmetry,induction
Solon's word:
"Theobservation of the numerous misfortunes that attend all conditions forbids usto grow insolent upon our present enjoyments, or to admire a man's happinessthat may yet, in course of time, suffer change. For the uncertain future hasyet to come, with all variety of future; and him only to whom the divinity has[guaranteed] continued happiness until the end we may call happy."
Four layers of meanings:
- Which came with the help of luck could be taken away by luck (and often rapidly and unexpectedly at that).
- Things that come with little help from luck are more resistant to randomness.
- The problem of induction (the black swan or the rare event).
- It does not matter how frequently something succeeds if failure is too costly to bear (skewness issue).
One: if you are so rich, why are not you so smart?
Nero and John. Nerotakes so little risk in his trading career that there could have been very fewdisastrous outcomes.
Two: a bizarre accounting method
$ 10 million earnedthrough Russian roulette does not have the same value as $10 million earnedthrough the diligent and artful practice of dentistry.
Reality is far morevicious than Russian roulette.
- It delivers the fatal bullet rather infrequently, like a revolver that would have hundreds, even thousands of chambers instead of six. After a dozen tries, one forgets about the existence of a bullet, under a numbing false sense of security.
- Unlike Russian roulette, one does not observe the barrel of reality.
Part of conventionalwisdom favors things that can be explained rather instantly and in a nutshell.However, common sense is nothing but a collection of misconceptions acquired byage 18. what sounds intelligent in a conversation or a meeting, or particularlyin the media, is suspicious.
Three: a mathematical mediation on history
Historicaldeterminism: we think that we would know when history is made; we believe thatpeople who, say, witnessed the stock market crash of 1929 knew then that theylived an acute historical event, and that should these events repeatthemselves, they would know about such facts. Life for us is made to resemblean adventure movie, as we know ahead of time that something big is about tohappen. It is hard to imagine that people who witnessed history did not know atthe time how important the moment was. Somehow all respect we may have forhistory does not transfer well into our treatment of the present.
Here is the math,supposing that the dentist invest his money into Treasury bills, the expectedrate of return is 15% with a 10% error rate per annum (volatility). It meansthat out of 100 sample paths, we expect close to 68 of them to fall within aband of plus and minus 10% around the 15% excess return, i.e., [5%, 25%].
A 15% return with a10% volatility (or uncertainty) per annum translate into a 93% probability ofmaking money in any given year. Here is the table of the probability of makingmoney at different scales.
| Scale | Probability |
| 1 year | 93% |
| 1 quarter | 77% |
| 1 month | 67% |
| 1 day | 54% |
| 1 hour | 51.3% |
| 1 minute | 50.17% |
| 1 second | 50.02% |
A few conclusionsfrom the dentist's story:
- Over a short time increment, one observes the variability of the portfolio, not the returns. In other words, one sees the variance, little else. I always remind myself that what one observes is at best a combination of variance and returns, not just returns.
- Our emptions are not designed to understand the point. The dentist did better when he dealt with monthly statements rather than infrequent ones. Perhaps it would be even better for him if he limited himself to yearly statements.
- When I see an investor monitoring his portfolio with live prices on his cellular telephone or his PalmPilot, I smile and smile.
Four: Randomness, nonsense, and the scientificintellectual
Alan Turing,Turing's test:
- A computer can be said to be intelligent if it can (on average) fool a human into mistaking it for another human.
We need to berational and scientific when it comes to markers and matters ruled byrandomness.
We do not need to berational and scientific when it comes to the details of our daily life - onlyin those that can harm us and threaten our survival.
If I'm going to befooled by randomness, it better be of the beautiful (and harmless) kind.
Five: Survival of the least fit, can evolution befooled by randomness?
Acute successfulrandomness fool
A review of marketfools of randomness constants
- An overestimation of the accuracy of their beliefs in some measure, either economic or statistical.
- A tendency to get married to positions. Loyalty to ideas is not a good thing for traders, scientists, or anyone.
- The tendency to change their story.
- No precise game plan ahead of time as to what to do in the event of losses.
- Absence of critical thinking expressed in absence of revision of their stance with "stop losses".
- Denial.
Six: Skewness and asymmetry
Frequency andprobability:
| Event | Probability | Outcome | Expectation |
| A | 999/1000 | $1 | $0.999 |
| B | 1/1000 | -$10,000 | -$10.00 |
| | | Total | -$9.001 |
The expectation is aloss of close to $9. The frequency or probability of the loss, in and byitself, is totally irrelevant; it needs to be judged in connection with themagnitude of the outcome.
Odds are that we would make money by betting on eventA, but it is not a good idea to do so.
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